I do not know if I can use the 'left' tongue ever in a way that is comparable to my normal 'right' tongue. My tongue is perfectly normal in most aspects besides never have been able to roll my tongue sides up or extrude it out very far. The more I play with it however the more it feels that I have areas that I do not control well. My tongue has always been the relatively small piece that tastes and hurts if I happen to bite it.
The image in my mind has always been that I have one tongue with a left and right side. I now feel that was an illusion created by the dominance of the right tongue in the mechanics of speech. It is not just the tongue that was not activated, it was the use of my left eye ,face, tongue, and throat. There is probably an audio component as well. I learned to communicate to another person's right side with my right side. It is how I relate to to other people. My left side is underdeveloped, not currently capable, bound by the habits that I have acquired over a lifetime.
However, I think there was an organic process that I used to learn the mechanics of speech with the right tongue. I believe it was acquired through mimicking and feedback. That process may be available for my left tongue but in a sense I have to learn to be 'left' instead of 'right'.